Receiver having analog and digital video modes and receiving method thereof

ABSTRACT

In a receiver having both an analog video service mode and a digital video mode, when the analog video mode is selected according to a mode selection signal indicating that a television channel is for the analog video mode or the digital video mode, a large-capacity memory used for the digital video-decoding may also be used as a frame memory for Y/C separation and post-processing, for enhancing picture quality, improving the efficiency of the memory and reducing the cost of a system.

This is a division of Application No. 08/719,626 filed Sep. 25, 1996,now U.S. Pat. No. 5,926,228.

BACKGROUND OF THE INVENTION

The present invention relates to a receiver having analog and digitalvideo modes and a receiving method therefor, and more particularly, to areceiver sharing a memory for digital television signal processing in ananalog video mode, and to a receiving method therefor.

The digital video mode is to receive television signals, digitallyprocessed by the MPEG (Moving Picture Experts Group) standards from atransmitter such as a broadcasting station, and the analog video mode isto receive signals analog-processed by a conventional broadcastingmethod such as NTSC, PAL or SECAM. While a set-top-box for decoding abitstream coded by MPEG-2, or a digital television including aset-top-box are being developed, conventional analog video service isstill overwhelmingly predominant. In answer to this situation, atelevision receiver having both analog and digital video modes isneeded. Such an analog and digital video mode television receiverrequires 8-32 Mb of memory for digital television signal decoding. Thismemory, however, is idle (i.e., unused) when the analog video mode isselected.

In an analog receiver having an analog video mode, as shown in FIG. 1, atuner 11 selects a desired television channel signal among receivedanalog television channel signals, to output an intermediate frequencysignal. A channel demodulator 12 amplifies and demodulates theintermediate frequency signal of the channel selected by tuner 11.(While the amplified and demodulated signal is separated into audio andvideo signals, only the video portion will be described for the sake ofsimplifying the drawings and description.) A luminance/chrominance (Y/C)separator 13 separates the video signal output from channel demodulator12 into luminance (Y) and chrominance (C) signals, using a correlationbetween a current line and its adjacent ones and/or between the previousframe and a current frame stored in a frame memory 14. The separatedsignals are stored in frame memory 14 and at the same time are input tothe display connector 15.

The display connector 15 converts the Y and C signals received from Y/Cseparator 13 into analog R, G and B signals and then outputs theconverted signals to a display 16 which is, for example, a picture tube.

Tuner 11, channel demodulator 12, Y/C separator 13 correspond to ananalog television signal processor 100. In addition, ananalog-to-digital converter can be included for converting the output ofchannel demodulator 12 into digital form in order to store it in framememory 14 as digital data, and a digital-to-analog converter forconverting the output of display connector 15 into analog form in orderto display it as an analog signal on display 16.

When a comb filter is used for the Y/C separation in a conventionalanalog television, a cross color or cross luminance phenomenon occursdue to insufficient Y/C separation. Accordingly, as shown in the circuitof FIG. 1, a frame memory is used for three-dimensional Y/C separationoften noted as frame comb filtering, to enhance picture quality.

Frame memory 14 may be also used for post-processing, for furtherenhancement of the picture quality after the Y/C separation. That is,edge components determined by the correlation between a current frameand a previous frame using frame memory 14, are emphasized. Most suchmethods for enhancing picture quality require a costly high-capacitymemory. Therefore, a method incorporating a limited memory is generallyused, even though it is not as effective.

FIG. 2 is a schematic block diagram of a conventional digital televisionfor receiving television signals coded by MPEG-2. In FIG. 2, a tuner 21selects a desired channel signal from television signals received froman antenna. The television signals received from the antenna are inputin an MPEG-2 packet structure.

According to an MPEG-2 format, the transmitting data has a system layerstructure consisting of packets of a 188-byte unit. The packet structureincludes a header having sync and side information and another regionhaving audio data, video data and user data. The video data iscompressed by an inter-picture encoding or intra-picture encodingtechnique. During the inter-picture encoding of predicted- andbi-directionally predicted picture data within each group of pictures(GOP) unit (fifteen pictures maximum) following an intra-picture, onlythe differences between the picture being encoded and another pictureare encoded. Each GOP includes intra-picture data which can beindependently coded without reference to any other picture data,predicted-picture data which can be coded from the precedingintra-picture data and the preceding predicted- pictures data by usingmotion compensation between adjacent pictures, and bi-directionallypredicted picture data which can be coded from a preceding intra- orpredicted- picture data and the following intra- or predicted-picturedata, using motion compensation, between adjacent pictures.

A channel demodulator 22 including a quadrature phase shift-keyingdemodulator, a Reed-Solomon decoder and a Viterbi decoder, converts adesired digital television channel signal which is output from tuner 21,into an MPEG-2 bitstream.

A system decoder 23 separates the MPEG-2 bitstream into audio and videodata streams. (As in the case of FIG. 1, the audio portion will not bedescribed, though it is assumed that an audio decoder and audio signalprocessor are provided for decoding and signal-processing the audiostream, and only the video signal process is shown and will bedescribed).

A video decoder 24 includes a variable-length decoder forvariable-length-decoding the video data stream output from systemdecoder 23, an inverse quantizer for inverse quantizing thevariable-length-decoded data, an inverse discrete cosine transform(IDCT) operator for performing IDCT operation, and motion compensatorfor computing motion-predicted data. Video decoder 24 reconstructs thecompressed data in order to display the original data on a display 27.The reconstructed video is converted into an analog RGB signal bydisplay connector 26 before being displayed on display 27.

A memory 25 is used for video-decoding, i.e., source-decoding, thedigital video data performed in video decoder 24.

Memory 25 includes a video buffering verifier (VBV) buffer (also call achannel buffer) for converting the constant bit rate of the video datastream output from system decoder 23 into a variable bit rate beforevariable-length-decoding, and frame buffers for reconstructing thepredicted and bi-directionally predicted pictures after compensating formotion by adding block data obtained by reading out a predetermined sizeof DCT blocks corresponding to a motion vector from previous frame dataand inverse-DCT data. Accordingly, memory 25 requires a capacity of 8 Mbto 32 Mb for the frames and VBV buffers in order to decode the videodata stream.

Tuner 21, channel demodulator 22, system decoder 23 and video decoder 24correspond to a digital television signal processor 200. Further, thecombination of digital television signal processor 200 and memory 25 isgenerally called a set top box (STB).

Since it is expected that the analog TV service such as NTSC, PAL willcontinue to exist, a consumer television system must have capability todisplay both analog and digital video services. Two methods thereforwill be described as follows.

Referring to FIG. 3, all processes for digital video service areperformed in an STB 210 and then the reconstructed video signal isapplied to a video input terminal of a conventional analog television110. Accordingly, digital video service can be received in the analogtelevision 110 also.

Referring to FIG. 4, a television having a conventional analog videomode is provided with the digital television signal processor 200 andthe memory 25, to thereby receive both analog video service and digitalvideo service.

Accordingly, as shown in FIGS. 3 and 4, the memory is used for analogtelevision signal processing, i.e., Y/C separation and post-processing,and an 8-32 Mb memory is used for decoding of digital video. When atelevision receives only analog video service, the memory of an 8-32 Mbfor digital video-decoding is not used. It is thus inefficient becausean existing resource within the television system cannot be used.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide areceiver having analog and digital video modes, wherein a memoryrequired for digital video signal decoding is commonly used for analogtelevision signal processing in an analog video mode.

It is another object of the present invention to provide a receivingmethod wherein a memory required for decoding a digital video signal iscommonly used for analog television signal processing in an analog videomode.

To accomplish the first object of the present invention, there isprovided a receiver having an analog video mode for receiving atelevision signal analog-processed by a predetermined analogbroadcasting method and a digital video mode for receiving a televisionsignal digital-processed by a predetermined digital signal format,comprising: first signal processing means for processing the receivedanalog television signal; second signal processing means for decodingthe received digital television signal; a memory for storing data inorder to decode the digital TV signal in the second signal processingmeans and process digitized analog television signal in the first signalprocessing means; generating means for generating a mode selectionsignal which represents either the analog video mode or the digitalvideo mode; and a memory controller for controlling the memory accordingto the mode selection signal in order to write/read the signal processedin the first signal processing means to/from the memory during theanalog video mode and write/read the digital TV signal to/from saidmemory during the digital video mode.

To accomplish the second object of the present invention, there isprovided a method for receiving a television signal analog-processed bya predetermined analog broadcasting method and a television signaldigital-processed by a predetermined digital signal format, comprisingthe steps of: (a) generating a mode selection signal which representseither analog video mode or digital video mode; (b) storing receiveddigital television signal according to the mode selection signal in amemory for digital video-decoding and decoding using the data stored inthe memory in digital video mode, and storing the received analogtelevision signal in the memory for digital video-decoding and readingthe data stored in the memory to process the data in the memory inanalog video mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail a preferred embodiment thereofwith reference to the attached drawings in which:

FIG. 1 is a block diagram of a conventional analog television;

FIG. 2 is a block diagram of a conventional digital television;

FIG. 3 is a schematic diagram of the conventional analog television withSTB;

FIG. 4 is a schematic diagram of a digital television having aconventional analog video mode;

FIG. 5 is a block diagram of a receiver having analog and digital videomodes according to a first embodiment of the present invention;

FIG. 6 is a detail view of the memory controller shown in FIG. 5;

FIG. 7 is a block diagram of the receiver having analog and digitalvideo modes according to a second embodiment of the present invention;

FIG. 8 is a block diagram of the receiver having analog and digitalvideo modes according to a third embodiment of the present invention;

FIGS. 9A through 9C illustrate modifications of the third embodimentshown in FIG. 8;

FIG. 10 is a block diagram of the receiver having analog and digitalvideo modes according to a fourth embodiment of the present invention;

FIG. 11 is a detail block diagram of an analog processor shown in FIG.10; and

FIGS. 12A through 12C are modifications of the fourth embodiment shownin FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The structure and operation of the analog and digital television signalprocessors 100 and 200 in FIG. 5 are the same as those in FIGS. 1 and 2.Therefore, no further description will be given.

Referring to FIG. 5, a controller 310 determines whether an inputchannel key is a television channel processed by a conventional analogmethod (an analog television channel) or a television channel digitallyencoded by MPEG-2 (a digital television channel), and outputs to amemory controller 320 a mode selection signal for either an analog ordigital video mode. According to the mode selection signal, memorycontroller 320 selects one output among those processed in analogtelevision signal processor 100 and digital television signal processor200, to store the selected output in a memory 330, or read the datastored in memory 330 to supply the data to either analog televisionsignal processor 100 or digital television signal processor 200.

In the analog video mode, the signal processed in analog televisionsignal processor 100 is displayed on a display 360 through a multiplexer340 and a display connector 360, and in the digital video mode, thesignal processed in digital television signal processor 200 is displayedon display 360 through multiplexer 340 and display connector 350.

Multiplexer 340 supplies the video signal selected according to a modeselection signal output from controller 310 to display connector 350.

In the analog video mode, memory 330 is used as the frame memory (or afield memory) for the Y/C separation and post-processing as describedreferring to FIG. 1. In the digital video service mode, on the otherhand, memory 330 is used as the VBV buffer for converting thetransmission rate and as the frame buffer for motion compensation, asdescribed referring to FIG. 2.

FIG. 6 is a detailed view of the memory controller 320 shown in FIG. 5.

Referring to FIG. 6, input and output lines include a data line forreading or writing data to and from memory 330, an address line and amemory control line such as an enable.

The memory controller 320 includes a plurality of multiplexers320.1-320.n for switching, wherein first input terminals a1-an of eachmultiplexer are respectively connected to the input/output (I/O) linesof the digital television signal processor 200, second input terminalsc1-cn are respectively connected to the I/O lines of the analogtelevision signal processor 100, and fix terminals b₁ -b_(n), arerespectively connected to the I/O lines of memory 330.

Accordingly, input and output lines of memory 330 are connected to inputand output lines of the analog television signal processor 100 when themode selection signal indicates the analog video mode, in order to usememory 330 as a frame buffer for Y/C separation and post-processing.Conversely, input and output lines of memory 330 are connected to inputand output lines of the digital television signal processor 200 when themode selection signal indicates the digital video mode, in order to usememory 330 as the VBV buffer for converting transmission rate and as theframe buffer for motion compensation.

In FIG. 7, a receiver sharing a memory for both analog and digital modesusing a bus-control method, is shown.

In the bus-control method, function control portions are connected to acontroller 410 (microcomputer) through two common bus lines, i.e., dataand clock lines, which allow bi-directional data transmission and areconnected to a data output terminal or terminals and a clock outputterminal of the controller. When the controller 410 transmits an addressand data over the bus lines and the transmitted address corresponds tothat of a given function control unit. The address function control unitis operated in accordance with the transmitted data. Accordingly, thebus-control method reduces the burden of the controller and decreasessignal-processing time.

Referring to FIG. 7, a controller 410 determines whether an inputchannel key is an analog television channel or a digital televisionchannel. When the selected channel is an analog television channel,controller 410 transmits the corresponding mode selection data via thedata line to analog television signal processor 100 and a memory 420 inorder to operate analog television signal processor 100 and memory 420.When the selected channel is a digital television channel, controller410 transmits the corresponding mode selection data via the data line todigital television signal processor 200 and memory 420 in order tooperate digital television signal processor 200 and memory 420.

Memory 420 is used as the frame memory for the Y/C separation andpost-processing when the analog video mode is selected, where currentframe data processed in analog television signal processor 100 iswritten in memory 420 through data lines, and previous frame data storedin memory 420 is transmitted to analog television signal processor 100through the data lines. Memory 420 is also used as the VBV buffer fortransmission rate conversion and as the frame buffer for motioncompensation when the digital video mode is selected, where dataprocessed in digital television signal processor 200 is stored in memory420 through the data lines, and previous data stored in memory 420 istransmitted to digital television signal processor 200 through the datalines.

Signals processed in the analog television signal processor 100 and thedigital television signal processor 200 according to the mode selectionsignal output from controller 410, are switched by multiplexer 430 andthen displayed on a display 450 through a display connector 440.

FIG. 8 is a block diagram of the receiver having analog and digitalvideo modes according to a third embodiment of the present invention.The function of the memory controller consisting of hardware in FIG. 5,that is, the function of selecting analog television signal processor100 or digital television signal processor 200 according to the modeselection signal, is programmed, and a memory 519 is alternately usedfor digital video-decoding and analog television signal processing suchas Y/C separation and post-processing.

Referring to FIG. 8, a first tuner 511 selects only a desired channelsignal among analog television channel signals transmitted through anantenna for receiving analog television channels, to output anintermediate frequency signal.

A first channel demodulator 512 amplifies the intermediate frequencysignal of the channel selected from the first tuner 511, and outputs avideo signal.

An analog-to-digital converter 513 converts the video signal output fromthe first channel demodulator 512 into digital form.

Meanwhile, a second tuner 514 selects a desired channel signal amongdigital television channel signals coded according to MPEG-2 andtransmitted through an antenna for receiving digital televisionchannels. A second channel demodulator 515 outputs the desired digitaltelevision channel signal output from second tuner 514 as an MPEG-2bitstream, and a system decoder 516 extracts only a video data streamfrom the MPEG-2 bitstream.

A controller 517 determines whether the input channel key is an analogtelevision channel or a digital television channel in order to output amode selection signal indicating the proper mode, i.e., the analog videomode or the digital video mode.

A microprocessor 518 receives the mode selection signal to select eitherthe output of the analog-to-digital converter 513 connected to a firstinput port or the output of the system decoder 516 connected to a secondinput port. That is, in an analog video mode, microprocessor 518 selectsa digitized analog television channel signal output from theanalog-to-digital converter 513, and then either writes in a memory 519or reads from memory 519 using the instructions of a predeterminedprogram, to perform Y/C separation and post-processing. Here, memory 519is used as a frame memory for the Y/C separation and post-processing.

As shown in FIG. 8, in addition to having signals received using firstand second input ports of the microprocessor 518, a multiplexer can beconnected to an input port to switch the two inputs in order to use onlyone input port of the microprocessor 518. The above modifications can beused for embodiments of FIGS. 9A through 9C, FIG. 10 and FIGS. 12Athrough 12C.

Meanwhile, a display connector 520 converts digital data output frommicroprocessor 518 into analog form, to display analog R, G and Bsignals on display 521. The display connector can be called a signalconverter.

The microprocessor 518 can calculate at a high speed, but a specificfunction such as inverse DCT which requires high-speed operation can berealized by hardware.

FIGS. 9A through 9C are modifications of the third embodiment shown inFIG. 8.

A microprocessor 522 shown in FIG. 9A, receives a digitized analogtelevision channel signal which is output from analog-to-digitalconverter 513 in analog video mode, to thereby perform Y/C separationand post-processing using memory 519 as described in FIG. 8.

Also, microprocessor 522 receives a MPEG-2 bitstream from second channeldemodulator 515 in digital video mode and then a video data stream isextracted from MPEG-2 bitstream under control of controller 517 andoutput to a video decoder 523. Video decoder 523 reconstructs video datastream from the extracted video data stream.

The microprocessor 522 provides a memory connection path so that videodecoder 523 uses memory 519 as a VBV buffer, a frame buffer and adisplay buffer.

A multiplexer 524 selects one of digitized analog signals, which areoutput from microprocessor 522 according to the mode selection signaloutput from controller 517 and reconstructed data in video decoder 523.

A microprocessor 525 shown in FIG. 9B performs Y/C separation andpost-processing in analog video mode as described in FIG. 9A, and MPEG-2system decoding and video-decoding in digital video mode. That is, inthe case of digital video mode, a video data stream is extracted fromMPEG-2 bitstream output from the second channel demodulator 515 and thenvideo data is reconstructed from the extracted video data stream bymicroprocessor 525.

A microprocessor 527 shown in FIG. 9C performs a memory control functionfor sharing memory 519 in analog mode and digital video mode and Y/Cseparation and post-processing in analog mode as described in FIGS. 9Aand 9B.

Meanwhile, in digital video mode, MPEG-2 system decoding andvideo-decoding are performed by a system and video decoder 526. Also, amultiplexer 528 supplies one of digitized analog signals output frommicroprocessor 527 according to the mode selection signal of controller517 and reconstructed video data output from system and video decoder526, to display connector 520.

FIG. 10 is a block diagram of a receiver having analog and digital videomodes according to a fourth embodiment of the present invention. Here,operation of a first tuner 611, a first channel demodulator 612, asecond tuner 614, a second channel demodulator 615, a system decoder616, a display connector 620 and a display 621 is the same as thatdescribed in FIG. 8.

In the third embodiment shown in FIG. 8, the memory control function isprogrammed into a microprocessor 618. However, in the fourth embodiment,the analog television signal processing such as three-dimensional Y/Cseparation or post-processing is analog processor 613 separated frommicroprocessor 618. Analog processor 613 is provided with an A/Dconverter 701, an analog TV signal processor 702 and a D/A converter703, as shown in FIG. 11.

In A/D converter 701, the channel demodulated signal output from firstchannel demodulator 612 of FIG. 10 is converted into digital data. Thedigital data is then received by an analog TV signal processor 702 andfurther stored in a memory 619 through microprocessor 618 operated as amemory controller. The analog TV signal stored in memory 619 is used bythe analog TV signal processor 702 for Y/C separation orpost-processing. The output processed by the analog TV signal processor702 is temporarily stored in memory 619 until being read out, and isconverted into analog signal in D/A converter 703.

Meanwhile, in case of digital video service, MPEG-2 bitstream is decodedinto a video data stream in the system decoder 616 and the video datastream is reconstructed to video data by microprocessor 618. Thereconstructed data is converted into analog signal by the D/A converter623.

According to the mode selection signal output from the controller 617where a mode is determined by a received channel key, a multiplexer 622selects an analog TV signal processed in the analog processor 613 or ananalog video signal output from the D/A converter 623.

The display connector 620 of FIG. 10 receives data converted into analogsignal and then converts the data into R, G and B signals, to therebyoutput the R, G and B signals to display 621. In a modification thereof,display connector 620 can be realized by uniting one of components ofanalog processor 613, i.e., a digital-to-analog converter 703 anddigital-to-analog converter 623. Here, the multiplexer 622 convertsreceived digital signals into analog signals, and then outputs analog R,G and B signals into display 621. The above modification is applied toFIGS. 12A, 12B and 12C.

Meanwhile, the embodiment of FIG. 10 can be slightly modified dependingon the extent of implementing MPEG decoding by software using themicroprocessor 618.

FIGS. 12A through 12C are modifications of the fourth embodiment shownin FIG. 10, where functionally identical portions are given by the samereference numerals as those of FIG. 10.

The microprocessor 801 shown in FIG. 12A performs only control of thememory 619. The MPEG-2 bitstream decoding and video data stream decodingare performed by a system and video decoder 802 outside of themicroprocessor 801.

A microprocessor 803 shown in FIG. 12B performs both MPEG-2 bitstreamdecoding and video data stream decoding.

A microprocessor 804 shown in FIG. 12C performs MPEG-2 bitstreamdecoding. However, video data stream decoding is performed by a videodecoder 805 external to the microprocessor 804.

According to the present invention, when a receiver for receiving bothanalog video service and digital video service processes a receivedanalog television channel, a large-capacity memory (as that for digitalvideo decoding) is commonly used as a memory for processing an analogtelevision signal, so that memory efficiency is enhanced and system costis reduced.

What is claimed is:
 1. A receiver having an analog video mode forreceiving television signals analog-processed by a predetermined analogbroadcasting method and a digital video mode for receiving televisionsignals digitally processed by a predetermined digital signal format,comprising:controlling means connected to common bus lines including atleast one data line and a clock line for generating mode selection datawhich represents one of said analog video mode and said digital videomode; first signal processing means connected to said common bus lines,for signal-processing an analog television signal according to the modeselection data; second signal processing means connected to said commonbus lines, for decoding a digital television signal according to themode selection data; and a memory connected to said common bus lines,for decoding the digital television signal from said second signalprocessing means, storing data processed in said first signal processingmeans according to said mode selection data for representing said analogvideo mode, and for supplying stored data to said first signalprocessing means.
 2. The receiver according to claim 1, wherein saidfirst signal processing means comprises:a first tuner for selecting achannel among received analog television channels, to output anintermediate frequency signal; a first channel demodulator foramplifying and demodulating said intermediate frequency signal of thechannel selected by said first tuner to output a video signal; and aluminance/chrominance separator for separating said video signal outputfrom said first channel demodulator into a luminance (Y) signal and achrominance (C) signal using correlation between adjacent picturesstored in said memory and between adjacent lines stored in said memory.3. The receiver according to claim 2, further comprising apost-processor for post-processing said luminance signal for enhancingpicture quality.
 4. The receiver according to claim 2, wherein, in saidanalog video mode, said memory is used as a frame memory for storingdata output from said first channel demodulator in a picture unit anddata input from said post-processor in a picture unit.
 5. The receiveraccording to claim 2, wherein, in said analog video mode, said memory isused as a frame memory for storing data output from said first channeldemodulator in a picture unit.
 6. The receiver according to claim 1,wherein said first signal processing means comprises:a first tuner forselecting a channel among received analog television channels, to outputan intermediate frequency signal; a first channel demodulator foramplifying and demodulating said intermediate frequency signal of thechannel selected by said first tuner and for outputting a video signal;and a post-processor for post-processing using said video signal outputfrom said first channel demodulator and data stored in said memory. 7.The receiver according to claim 6, wherein, in said analog video mode,said memory is used as a frame memory for storing data output from saidfirst channel demodulator in a picture unit.
 8. The receiver accordingto claim 1, wherein said second signal processing means comprises:asecond tuner for selecting a channel signal among received televisionsignals coded by the digital signal format; a second channel demodulatorfor channel-decoding the channel signal output from said second tuner; asystem decoder for outputting a video data stream from a channel-decodedsignal output from said second channel demodulator; and a video decoderfor reconstructing video data from said video data stream.
 9. Thereceiver according to claim 8, wherein, in said digital video mode, saidmemory is used as a channel buffer for converting the transmission rateof a constant bit rate into a variable bit rate for video-decoding andas a frame buffer for motion compensation.
 10. The receiver according toclaim 1, further comprising:switching means for selecting one of theoutput signals from said first signal processing means and said secondsignal processing means according to said mode selection data; anddisplay control means for displaying the signal selected by saidswitching means on a display.